1. Field
The following description relates to a method and apparatus for generating a tracking error signal without using a side beam.
2. Description of Related Art
There are various methods for generating a tracking error signal from an optical disc. In a push-pull (PP) method, an offset is generated according to a lens shift. In order to cancel the offset, a differential PP (DPP) method is used and is based on a side beam. The DPP method cancels an offset generated by a shift of the tracking error signal according to a lens shift, by amplifying a side beam PP (SPP) and generating a direct current (DC) offset that has the same size and an opposite phase from a main beam PP (MPP).
When the DPP method is applied, an optical pickup splits light emitted from a light source into three beams, for example, a main beam and two side beams, using a grating. In this example, a photodetector may be used to generate a PP signal by detecting the main beam and the two side beams irradiated on and reflected from an optical disc.
As such, in order to use the DPP method, an optical structure and a circuit structure, which are configured to generate and detect a side beam, are required. However, the generation of the side beam typically deteriorates the power of the main beam used to record/reproduce on/from the optical disc. As a result, the DPP method causes additional power consumption while reducing the quality of the main beam.